1. Field of the Invention
This invention relates to a device for supporting a lift roll for a fork lift truck of the type in which the thrust in the fore and aft direction and in the transverse direction is supported solely by a lift roll. More particularly, it relates to a device for supporting the lift roll of the type in which the thrust in the transverse direction is supported by that the lateral side of the outer race abuts on a pressure receiving section formed on a web of a mast and in which the contact pressure of the lateral side of the outer race with respect to the pressure-receiving section is adjusted by an adjustment screw.
2. Prior Art
FIG. 1 shows a typical prior-art lift roll 4 of the type in which a transverse thrust is received by abutment of the lateral surface of an outer race 7 on a pressure-receiving portion 8c formed on a web 8b of an inner mast 8. The lift roll 4 is mounted to a roll pin 3 projectingly mounted as by welding to a rear plate 2 of a lift bracket 1 as shown. That is, an inner race 5 is fitted on the roll pin 3 for movement axially, while an outer race 7 is fitted on the inner race 5 for rotation, this outer race 7 being adapted for rolling longitudinally on a flange section 8a as the lateral side of the outer race abuts on a pressure-receiving portion 8c formed on the web 8b of the inner mast 8. The contact pressure of the lateral side of the outer race on the pressure-receiving portion 8c is usually adjusted by a shim 25. The adjustment system of this type is shown for example in the Japanese Patent Publication No. 32819/1973.
Another adjustment system using a screw is shown in FIG. 2 in which the inner race 5 is fitted with a bottom plate 5a one lateral side of which is closed by a plate. The bottom plate 5a is thrusted towards the inner mast 8 by an adjustment screw 9 threadedly passed through central openings of the roll pin 3 and of the rear plate 2 of the lift bracket 1. This adjustment system is described for example in the Japanese Utility Model Publication No. 31674/1984.
In the above described conventional lift rolls, the inner race 5 can be extracted from the roll pin 3 in both the adjustment system by the shim 25 and the adjustment system by the adjustment screw 9. Thus, in case when flexure or distortion has occurred between the inner mast 8 and the lift bracket 1, there is the risk of the lift roll 4 dropping off the roll pin 3 or the lift roll 4 being tilted to cause locking. This phenomenon of flexure or distortion between the inner mast 8 and the lift bracket 1 is likely to occur in case of application of a partialized load, that is, when the load is clamped in the acutely partialized state such as in the course of the material handling operation employing a rotary clamp, and the load is then relocated after inverting the load through 90.degree. or 180.degree.. Since the left and right side inner masts 8 are arranged in the form of a letter eight narrowed at the ends in order to eliminate vibrations in the raised state, the lift roll 4 is liable to drop off the roll pin 3 when the lift bracket 1 is tilted relative to the inner masts 8, as shown in FIG. 4. There is also, as shown in FIG. 3, the risk that the lift roll 4 be moved in the dropping direction relative to the roll pin 3 while being tilted and locked between the inner masts 8 and the roll pin 3 such that rotation thereof is inhibited.
It is therefore an object of the present invention to provide a device for supporting a lift roll for a fork lift track that is free from the above described disadvantages of the prior art device.